I've had a few similar types of people sit next to me on flights, in both coach and the premium cabins - drunks, obnoxious, rude, nosy, assorted DWIA types, etc. Normally I don't encourage conversations with a seat mate, but have done so on the rare occasion.

I don't like being interrogated, period.

If a stranger on an airplane starts with I deem to be interrogation, I will politely ask that they refrain from asking such questions, and advise them that I want to read and/or relax for the rest of the flight. This usually shuts them up. I would NEVER continue a conversation with someone who made such condescending comments and/or asked personal questions.

It sounds like the obnoxious seatmate in this situation was simply craving attention and was looking for an audience.